====== SMTP Protocol ======

  S: 220 smtp.example.com ESMTP Postfix
  C: HELO relay.example.org
  S: 250 Hello relay.example.org, I am glad to meet you
  C: MAIL FROM:<bob@example.org>
  S: 250 Ok
  C: RCPT TO:<alice@example.com>
  S: 250 Ok
  C: RCPT TO:<theboss@example.com>
  S: 250 Ok
  C: DATA
  S: 354 End data with <CR><LF>.<CR><LF>
  C: From: "Bob Example" <bob@example.org>
  C: To: Alice Example <alice@example.com>
  C: Cc: theboss@example.com
  C: Date: Tue, 15 Jan 2008 16:02:43 -0500
  C: Subject: Test message
  C:
  C: Hello Alice.
  C: This is a test message with 5 header fields and 4 lines in the message body.
  C: Your friend,
  C: Bob
  C: .
  S: 250 Ok: queued as 12345
  C: QUIT
  S: 221 Bye
  {The server closes the connection}